“Brake-by-wire” brake systems for motor vehicles are more and more widespread in automotive technology. In addition to a brake master cylinder which can be actuated by the vehicle driver, brake systems of this type often include an electrically controllable pressure provision device, by means of which an actuation of the wheel brakes takes place in the “brake-by-wire” operating mode.
The international patent application WO 2011/029812 A1 has disclosed a “brake-by-wire” brake system having a brake master cylinder which can be actuated by brake pedal, a travel simulator and a pressure provision device. The wheel brakes are loaded with pressure by way of the pressure provision device in the “brake-by-wire” operating mode. In a fallback operating mode, the wheel brakes are loaded with pressure by means of the brake master cylinder which is actuated by brake pedal.
DE 195 13 37 B4 has disclosed an electromechanically actuable pressure modulator having a working piston which can be actuated by way of an electric motor. The working chamber is configured as a stepped bore, in which an annular piston with a pressure medium passage is guided axially movably in the region of the smaller bore step. A valve is arranged on the end face of the working piston, which valve closes the pressure medium passage within the annular piston upon actuation of the working piston. To this end, a coaxial orientation of the annular piston and the working piston is necessary. Furthermore, the pressure modulator includes a further floating piston which is arranged in parallel offset with respect to the annular piston. On account of the three pistons, the known pressure modulator is comparatively complicated to manufacture and is of comparatively large construction.
It is an object of the present invention to provide an electrically controllable pressure provision device which is suitable for a hydraulic motor vehicle brake system, which pressure provision device is improved with regard to the overall size and the manufacturing costs. Here, the pressure provision device is to be as reliable as possible with regard to leaks, in order thus to also fulfill the safety requirements for a motor vehicle for autonomous driving.